This invention relates generally to electro-luminescent lamp panels and, more particularly, to a resonant circuit for recovering energy stored in these panels that would otherwise be dissipated during the discharge cycle of a drive circuit.
Electro-luminescent lamps act as capacitors, electrically. These lamps store energy, as do all capacitors, in the form of an electrical voltage charge. In the normal electro-luminescent lamp driver circuit, this charge is dissipated, and therefore lost, during the discharge cycle of operation.
Electro-luminescent lamp driver circuits are well known in the prior art, exemplary of which are the Supertex HV803 and the Toko TK659XX. A typical one of these circuits is illustrated in FIG. 1. In that circuit, components L1, S0, D1, and C1 constitute a high voltage boost or step-up converter which receives a low voltage (less than 6 volts) and boosts it to between 20 and 100 volts on the capacitor C1. Components S1, S2, S3, and S4 constitute an H-bridge circuit that is used to commutate the high DC voltage on capacitor C1 into a high AC voltage across an electro-luminescent lamp capacitor (C lamp) that is about twice the DC voltage on capacitor C1. This AC voltage charges and discharges the capacitor C lamp, with the energy stored in the capacitor C lamp being dissipated in components S3 and S4 of the H-bridge during the discharge cycle.
It would be advantageous to recover this energy, existing in the form of charge at high voltage, from the electro-luminescent lamp capactior C_lamp, and reuse it, thus making the entire electro-luminescent lamp driving system more efficient. Accordingly, the present invention is directed to a method utilizing capacitor C_lamp in a resonant circuit to implement the recovery of this otherwise lost energy, which is significant in the case of large electro-luminescent lamps that are driven to higher voltages.